1. Field of the Invention
The present invention provides an enzyme preparation containing transglutaminase and a method for producing food products using the same. More specifically, the invention relates to an enzyme preparation containing 1) transglutaminase, 2) collagen and 3) an acidic or alkaline substance shifting the pH of the enzyme preparation when dissolved in a solution to a pH range where the expression of the transglutaminase activity is suppressed, and a process for producing food products using the enzyme preparation.
2. Discussion of the Background
Heretofore, there have been numerous reports of technique for applying effects of a crosslinking reaction in various proteins by transglutaminase in the fields of foods, medicinal products and chemical products. Among them, intensive research has been focused on a technique utilizing collagen (including gelatin, infra) and transglutaminase, in combination, thus engendering wide applicability in these technical fields.
For example, the following inventions have been reported: a method for producing modified collagen including a step of strengthening the inter-collagen molecular crosslinking with a transglutaminase (Japanese Patent No. 2897780); inventions of gelatin gel, gel-like foods and gelatin films with great thermal resistance and methods for producing the same (JP-A-6-98743, 7-227228 and Japanese Patent No. 2866746); and a method for producing restructured food with strong binding effects, using a combination of transglutaminase and collagen (JP-A-10-70961).
In addition to the field of food products, there have been reports about a collagen gel-type aromatic product with sufficient strength and thermal resistance, as well as a method for producing the same (JP-A-9-70428). As described above, the advantages obtained from the use of transglutaminase and collagen in combination has significant value in many fields of endeavor. Additionally, such a technique is advantageous.
Because collagen has extremely high reactivity with transglutaminase, however, the viscosity increases and gelation rate of solutions of transglutaminase and collagen in mixture are characteristically very rapid. Therefore, when producing gel-like food or restructured food various restrictions emerge during the production processes because the gelation of transglutaminase progresses immediately after transglutaminase is mixed with collagen.
When a solid food material is to be dispersed in a mixed solution of transglutaminase and collagen, for example, the dispersion procedure should be completed in a very short time frame until gelation starts. Accordingly, it is very difficult to produce a homogenous gel-like food at a mass scale.
As a method for producing restructured foods, a process is known where a paste-like material containing transglutaminase and collagen dissolved in water is added to a solid food material followed by mixing. When the gelation of the paste-like material is completed before the paste-like material is mixed in the solid food material, a food product with sufficient binding strength cannot be produced.
Further, collagen may sometimes be blended with curing agents and pickling liquids for use in the production of processed meat products such as ham, bacon and roasted pork. During the preparation of such pickling liquids, transglutaminase reaction with collagen progresses, disadvantageously, involving an increase in the viscosity to consequently prevent injection.
Therefore, to produce food products containing transglutaminase and collagen it is important that the transglutaminase reaction be tightly controlled during the production process. One method for suppressing the enzyme activity of transglutaminase is by dissolving transglutaminase in water at low temperature. This process utilizes the phenomenon that the transglutaminase activity is suppressed at low temperature. However, this process has an insufficient effect on the control of the physical properties. Additionally, such strict temperature control during the production process is not practical. Still further, gelation may be controlled by separately adding transglutaminase and collagen separately. However, such procedures are very laborious during the production process and not preferable.
In the production of restructured food alone, in addition to a process of adding a paste-like material of transglutaminase and collagen dissolved in water to a solid food material, a process of directly adding powdery or granular transglutaminase and collagen to a solid food material for binding has been previously described.
Enzyme preparations with a transglutaminase in blend in the related art are not preparations with wide applicability for use by any of the two processes above. Hence, an adhesive preparation with high applicability generating such highly satisfactory effects by any process, with no need to use a specific preparation for a specific production process, is strongly desired. Additionally, the enzyme preparation for binding comprising transglutaminase and collagen in blend as disclosed in JP-A-10-70961 can produce sufficient binding strength. At actual production sites, however, an enzyme preparation for binding generating stronger binding strength in a far shorter time period is needed.